'\" et
.TH SETBUF "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
setbuf
\(em assign buffering to a stream
.SH SYNOPSIS
.LP
.nf
#include <stdio.h>
.P
void setbuf(FILE *restrict \fIstream\fP, char *restrict \fIbuf\fP);
.fi
.SH DESCRIPTION
The functionality described on this reference page is aligned with the
ISO\ C standard. Any conflict between the requirements described here and the
ISO\ C standard is unintentional. This volume of POSIX.1\(hy2017 defers to the ISO\ C standard.
.P
Except that it returns no value, the function call:
.sp
.RS 4
.nf

setbuf(stream, buf)
.fi
.P
.RE
.P
shall be equivalent to:
.sp
.RS 4
.nf

setvbuf(stream, buf, _IOFBF, BUFSIZ)
.fi
.P
.RE
.P
if
.IR buf
is not a null pointer, or to:
.sp
.RS 4
.nf

setvbuf(stream, buf, _IONBF, BUFSIZ)
.fi
.P
.RE
.P
if
.IR buf
is a null pointer.
.SH "RETURN VALUE"
The
\fIsetbuf\fR()
function shall not return a value.
.SH ERRORS
Although the
\fIsetvbuf\fR()
interface may set
.IR errno
in defined ways, the value of
.IR errno
after a call to
\fIsetbuf\fR()
is unspecified.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
A common source of error is allocating buffer space as an ``automatic''
variable in a code block, and then failing to close the stream in the
same block.
.P
With
\fIsetbuf\fR(),
allocating a buffer of BUFSIZ bytes does not necessarily imply that all
of BUFSIZ bytes are used for the buffer area.
.P
Since
.IR errno
is not required to be unchanged on success, in order to correctly detect
and possibly recover from errors, applications should use
\fIsetvbuf\fR()
instead of
\fIsetbuf\fR().
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "Section 2.5" ", " "Standard I/O Streams",
.IR "\fIfopen\fR\^(\|)",
.IR "\fIsetvbuf\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<stdio.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
